INFLUENCE OF PROCESS PARAMETERS ON ANODIC PLASMA ELECTROLYTIC POLISHING OF Q235 LOW-CARBON STEEL IN (NH4)2SO4 ELECTROLYTE

The plasma electrolytic polishing (PEP) process on Q235 low-carbon steel anode in (NH4)(2)SO4 electrolyte was investigated, and its surface properties under different PEP conditions were evaluated. The surface roughness of PEP samples under different electrolyte concentrations, initial roughness, voltages and treating times were measured. The surface morphologies and compositions of typical PEP samples were analyzed, and their wettability and surface free energy under different polishing times were evaluated. It was found that the near-surface temperature of the steel sample raised quickly with increasing the voltage, and then remained at about 100 degrees C after 200V, which is beneficial to keep the microstructure and mechanical properties of Q235 low-carbon steel. Under the parameters of 3.0wt.% (NH4)(2)SO4 aqueous solution and applied voltage of 200V, the 8min PEP treatment could reduce the surface roughness of Q235 low-carbon steel from 2.100 mu m to 0.437 mu m. In addition, the polishing efficiency was the highest in the initial PEP stage, meanwhile, it also increased with the increase of initial roughness of the sample. After the PEP treatment, the contact angle of water on low-carbon steel decreased, and its surface free energy was slightly reduced. Moreover, the thickness of natural oxide film on Q235 low-carbon steel was reduced by about 30% after 8 min polishing treatment.